Abstract: In order to ensure the visual effect and unity of color mapping of multi-charts among the data with the same category,it is proposed to study the color assignment optimization problems on multi-charts,which introduces a score defined based on perception and harmony to guide the joint color assignment optimiza-tion.When given the data plotted with multi-charts and the color palette,first the quality of the color palette is evaluated.If the color palette is of high quality,the proposed method will directly optimize the color as-signment.Otherwise,the color palette needs to be optimized first.Several user studies are conducted to show that the proposed method can ensure the unity of multi-charts color mapping and improve the quality of visualization results.